The present invention relates to an armature assembly providing adjustment in the magnetic calibration of a tripping mechanism in a circuit breaker. In particular, the bias of a torsion spring is adjusted to bring the calibration of the tripping mechanism into the desired range.
Load centers and other electrical distribution devices are commonly used in residential, commercial, and industrial applications. Individual circuit interrupters are mounted within these devices to protect branch circuits against overload and fault conditions. Basically, circuit interrupters like circuit breakers and fusible switches comprise a pair of separable contacts, a spring-operated mechanism for effecting separation of the contacts, and a tripping mechanism or fuse which automatically releases the operating mechanism upon occurrence of an overload or fault condition. The tripping mechanism is calibrated to a desired range usually by adjusting an armature or yoke gap.
A problem can arise in calibrating the tripping mechanism. The armature/yoke gap provides only a limited range of adjustment and can fail to bring the calibration of the tripping mechanism into the desired range. There usually is no other mechanism for adjusting the calibration of the tripping mechanism. Particularly with thermal magnetic circuit breakers, there usually is no mechanism for adjusting the magnetic calibration. As a result, the magnetic spring force used by the tripping mechanism must be held to very tight tolerances, further complicating the manufacturing process.
The need arises to provide a second mechanism for adjusting the calibration of the tripping mechanism for a circuit breaker. In particular, a mechanism for adjusting the magnetic calibration of a circuit breaker terminal could provide a more broad range of adjusting the calibration of the tripping mechanism than is currently available. The manufacturing process can also be simplified by easing the tolerances needed by the parts comprising the tripping mechanism.
The present invention provides a bracket for an armature assembly providing adjustment of the magnetic calibration of a tripping mechanism in a circuit breaker using an adjustment screw. The tripping mechanism connects to a first pin supported within the interior of the circuit breaker. The bracket includes a channel defined by a pair of legs and a bight with opposing sides. Each of the legs has a hole for affixing therein the first pin connected to the tripping mechanism. A first tab and a second tab are fixedly connected to opposing sides of the bight. The first and second tabs are positioned parallel to one another and perpendicular to the opposing sides of the bight. The first and second tabs have a respective first and second hole that are threaded for receiving therein the adjustment screw so that rotating the adjustment screw adjusts the position of the bracket relative to the interior of the circuit breaker and rotates the first pin to calibrate the tripping mechanism.
The present invention provides an armature assembly for adjusting the magnetic calibration of a tripping mechanism in a circuit breaker includes a bracket having a channel defined by a pair of legs and a bight with opposing sides. A first tab and a second tab are fixedly connected to opposing sides of the bight. The first and second tabs are positioned parallel to one another and perpendicular to the opposing sides of the bight. The first and second tabs have a respective first and second hole that are threaded. A first pin rotatably connects to the tripping mechanism within the interior of the circuit breaker. The first pin is affixed across the legs of the channel. An adjustment screw has an elongated body with a top portion on one end and at the opposing end a bottom portion. The adjustment screw has a plurality of screw threads defining an exterior side wall of the elongated body along the bottom portion. The plurality of screw threads configured to releasably engage the threaded fastener component. A washer has an approximate donut shape defined by relatively flat opposing surfaces. The washer is rotatably affixed though its center to the adjustment screw. A spring has one end attached to the washer and a second end attached to the interior of the circuit breaker to provide a bias with a force adjustable as the washer is moved by rotating the adjustment screw.
The present invention also provides a method of adjusting the magnetic calibration of a tripping mechanism in a circuit breaker. The steps of the method include: connecting a bracket having first and second tabs with first and second holes that are threaded to a first pin rotatably connecting to the tripping mechanism within the interior of the circuit breaker; engaging an adjustment screw through the threaded holes in the bracket; biasing the adjustment screw and bracket against a spring; and rotating the adjustment screw to adjust the distance between the bracket and screw to correspondingly adjust the bias on the tripping mechanism.